A toxikológia a xenobiotikumok és az endogén fiziológiai folyamatok okozta mérgező hatások tudomá... more A toxikológia a xenobiotikumok és az endogén fiziológiai folyamatok okozta mérgező hatások tudománya. Empirikus előzményei visszavezetnek az emberré válás folyamatáig, hiszen eleink életben maradásának egyik fontos záloga volt az ehető és a mérgező növények, illetve állatok elkülönítése. Az emberiség fejlődésének kiteljesedő folyamatában a mérgek használata három fő területen jelent meg: 1) a vadászatban, majd a hadviselésben, 2) békeidőben az ellenfelek megmérgezésében, miután a rejtőzködő stratégia jellemzően előnyösebbnek bizonyult a nyíltan alkalmazott durva fizikai eszközöknél, és 3) a gyógyászatban az ellenmérgek, majd a betegségeket legyőző erős anyagok révén, de paradox módon az orvoslási segédlettel végrehajtott emberölést, vagyis az aktív eutanáziát is idesorolhatjuk. A XIX. század ipari forradalma az addig marginális foglalkozási ártalmakat népbetegséggé tette, majd a vegyipar forradalma és a műanyagok tömegtermelése a XXI. században globális környezeti katasztrófával fenyegeti az emberiséget. Ez a változás a humántoxikológia után az ökológiai toxikológia színrelépését eredményezte, ami már nem történelme, hanem jövője ennek a tudománynak.
Several biomarkers may be used to detect harmful exposure and individual susceptibility to cancer... more Several biomarkers may be used to detect harmful exposure and individual susceptibility to cancer. Monitoring of biomarkers related to exposure may have a significant effect on early detection of cell transformation, thereby aiding the primary prevention of various chronic and malignant diseases. Nurses who handle cytotoxic drugs are exposed to carcinogenic agents, which have the potential to interrupt the cell cycle and to induce chromosomal aberrations. The presence of high chromosomal aberrations indicates the need for intervention even when exposure to these carcinogens is low. Nationally representative samples of 552 nurses were investigated by a follow-up monitoring system. The measured biomarkers were clinical laboratory routine tests, completed with genotoxicological (chromosome aberrations [CAs] and sister chromatid exchanges [SCEs]) and immunotoxicological monitoring (ratio of lymphocyte subpopulations and lymphocyte activation markers) measured on peripheral blood lymphoc...
More than half of the Hungarian population is overweight or obese, therefore, non-alcoholic fatty... more More than half of the Hungarian population is overweight or obese, therefore, non-alcoholic fatty liver is a common problem. According to clinical experience, 20-30% of fatty liver cases is not related to alcohol, but can be linked to diabetes, obesity or metabolic syndrome. The authors studied the correlation between genotoxicity, immuntoxicity and non-alcoholic fatty liver among oil refinery workers. During this genotoxicological monitoring study the data of 107 exposed were compared to 67 controls. 36% of oil refinery workers had non-alcoholic fatty liver, while none of the selected, non-exposed controls had this abnormality. Chromosomal aberrations were elevated from 1.6% to 3.75% in the exposed group, immunotoxicological parameters were also changed, and CD71 positive B-cell ratio increased especially among subjects having non-alcoholic fatty liver. Non-alcoholic fatty liver can negatively influence the genotoxic effects of environmental hazards in workplaces. In the future thi...
Introduction 1.1 Environmental endogenous DNA damages Cancer development is a long-term, multiste... more Introduction 1.1 Environmental endogenous DNA damages Cancer development is a long-term, multistep process with a complex interplay between genes and environment. The magnitude of environmental effects depends on the presence or absence of genetic susceptibility of the subjects to certain cancer types. Molecular epidemiological studies in cancer have proved that besides target cell genetic instability, the presence of triggering environmental exposure is critical in cancer development [Albertini & Hayes 1997, Newby & Howard 2005]. The biomarker responses, exposure character and the route of exposure of different environmental factors (chemicals, physical agents and biological agents) are also important in causing tumors especially in the cases of occupational cancer [Ward 1995]. The EPA Guidelines for carcinogen Risk Assessment [EPA 2005] is based on the mode of action of chemicals, such as interaction with DNA, cytotoxicity, or binding to the receptors modifying signal pathways. There are several natural compounds-so called chemopreventive agents-which are able to modify the genotoxic or mutagenic response (Ames 1983) in different organisms. These vitamins, antioxidants, phytochemicals, micro nutrients are available on the market without knowing their mode of action. Mutagenesis caused by environmental chemicals or physical agents can be prevented by protection of the cell's DNA replication, increasing the repair capacity or delaying cell replication to allow enough time to make a complete repair of damaged cells. Antioxidants are able to protect the cells from oxidative stress, and stimulate the phase I reactions including oxidation, reduction, and hydrolysis of xenobiotics by the monoxigenase detoxicating key enzymes, such as CYP450 [Xu et al. 1996, Poulsen & Loft 1998]. These changes increase the polarity of these molecules and help to conjugate them in phase II to glucuronic acid, acetic acid and sulfuric acid which are the physiological ways to eliminate active metabolites that are genotoxic to the target cells. The best studied crucial early event in carcinogenesis is chromosomal aberration, including microsatellite instability, abnormal number of chromosomes (aneuploidy), gene amplification or the loss of heterozygosity of tumor suppressor genes. By reducing chromosomal mutation via chemoprevention, the cell may be able to survive the genotoxic effects without any permanent damage, or it is able to go through the physiological pathway of apoptosis, without mutation occurring in the P53 gene [Lowe & Lin 2000]. www.intechopen.com DNA Repair and Human Health 308 1.2 The role of DNA repair in gene-environmental interactions The measurement of UV-induced DNA repair is recommended in the risk assessment of environmental exposure to harmful chemicals (Reg. 440/2008/EC). Data obtained on prokaryota organisms suggest that exposure to chemicals as e.g. free oxygen radicals can interact with UV-induced DNA repair mechanisms (Chandor-Proust et al, 2008). Among the repair mechanisms existing in higher eukaryota, base excision repair (BER) seems to be the main mechanism involved in the removal of lesions produced by alkylation, deamination or oxidation (Rastogi et al, 2010). Orelli et al. (2009) demonstrated recently that nucleotide excision repair (NER) also plays an important role in the development of cisplatin resistance. UV-induced DNA damages can induce the so called three prime exonuclease1 (trex1), as a response to genotoxic stress. Beside thymine dimer production, UV irradiation can also produce reactive oxygen species. Benzo(a)pyrene (BaP) and hydrogen peroxide may, similarly to UV, induce the so-called three prime exonuclease1 (trex1) involved in the repair pathways of UV-induced DNA lesions, and cells deficient in trex1 show reduced recovery from UV and BaP replication inhibition, and increased sensitivity to towards genotoxins compared to the isogenic control (Christmann et al, 2010). These data suggest that both main mechanisms can be involved in the total repair of environmental chemical-induced genotoxic stress. Such mechanisms can probably explain the observed UDS reduction in some of our groups exposed to various chemicals but not UV. A second question is whether decreased UDS can be related to an increase in apoptotic capacity? Cells deficient in the repair of UV-induced DNA damage can be more susceptible to a G1 arrest after UV treatment than cells with normal repair capacity or those cells which have completed their DNA repair prior to movement from G1 to S phase (Geyer et al, 2000). Zampetti-Bosseler and Scott (1981) demonstrated a prolonged mitotic delay in repair deficient ataxia teleangiectasia and retinoblastoma fibroblasts after X-ray irradiation compared to normal human fibroblasts, also suggesting a general key role of cell cycle check points beside DNA repair in preservation of genome stability (Kaufman, 1995). Skin fibroblasts from derived ataxia teleangiectasia patients are also more sensitive to UVinduced mutagenesis than those taken from healthy subjects (Hannan et al, 2002), and their results suggested a relationship between cell cycle control and DNA repair pathways in human cells. Genotoxic chemicals can also delay cellular proliferation in DNA repairdeficient cell clones more significantly than in wild type cells, by interfering with DNA replication, thereby inducing DNA damage (Kyunghee et al, 2009). The recently discovered cell cycle checkpoint activation mechanisms are discussed in detail by Rastogi et al (2010). In the present study the so-called premature centromere division (PCD) was used as a cytogenetic indicator of abnormalities in cell cycle regulation (Méhes 1978, Vig, 1981, Major et al, 1999). PCD yields were increased among cytostatic drug producers, anesthesiologists using halothane, and in exposures to formaldehyde, benzene and PAHs. PCD can be involved in the pathomechanism of aneuploidy, it seems to be a possible manifestation of chromosome instability also in human chromosome breakage syndromes and it can be connected with carcinogenesis (for review, c.f. Major et al, 1999). 2. Cancer development and DNA repair We don't know exactly what the cause of cancer is; therefore we have several mechanisms and theories to explain it. One of them is shown in Fig.1. www.intechopen.com Application of UV-Induced Unscheduled DNA-Synthesis Measurements in Human Genotoxicological Risk Assessment 315 6. Analysis of biomarkers in blood samples Biomarkers for DNA damages and risk assessment Considering the basic mechanism of cancer development, the most acceptable predictors of cancer risks are the DNA-damage biomarkers (see Table 3.). These damages can be provoked by exogenous or end o g e n o u s a g e n t s w h e n D N A r e p a i r o r m i s-r e p a i r i s i n dysfunction. The unrepaired DNA damage can reduce the basic cell functions eg. maintenance of genetic integrity, triggering of cell cycle arrest, apoptosis, uncontrolled growth and other functionalities. Ultimately, damaged repair capacity leads to an increase in somatic mutations and cancer. Any living cells Mitochondrial DNA mutation Any living cells Point mutation (HPRT) Any living cells Nuclear p53 Lymphocytes, germ cells DNA-adducts and oxidation, methylation Any living cells Telomere shortening Tumor cells, lymphocytes, germ cells Aneuploidy Lymphocytes, bone marrow cells Micronucleus assay Tumor cells, lymphocytes, germ cells Chromosomal aberrations Any living cells, germ cells DNA strand breaks (SGE or Comet assay) Lymphocytes, hepatocytes Unscheduled DNA synthesis (UDS) Target cells Methods Any living cells Mitochondrial DNA mutation Any living cells Point mutation (HPRT) Any living cells Nuclear p53 Lymphocytes, germ cells DNA-adducts and oxidation, methylation Any living cells Telomere shortening Tumor cells, lymphocytes, germ cells Aneuploidy Lymphocytes, bone marrow cells Micronucleus assay Tumor cells, lymphocytes, germ cells Chromosomal aberrations Any living cells, germ cells DNA strand breaks (SGE or Comet assay) Lymphocytes, hepatocytes Unscheduled DNA synthesis (UDS)
At the National Institute of Chemical Safety we have surveyed the immunological status of donors ... more At the National Institute of Chemical Safety we have surveyed the immunological status of donors from the oil industry, health services, and metallurgy exposed to different immunotoxic compounds. Their data were compared to those of healthy, non-exposed controls. Our aim was to study the relationship between immunotoxic exposure and immune function, and to establish a system of immunological parameters by which chemical exposure can be specifically monitored. Subpopulations and activation of lymphocytes was measured by flow cytometry, using immunophenotyping of peripheral blood lymphocytes. In the groups exposed to immunotoxic compounds we found an increase in helper, and a decrease in cytotoxic T lymphocytes, leading to a shift in Th/Tc ratios. These phenomena are not substance specific, but relate to chemical exposure. The lymphocytes of exposed groups showed a higher proportion of activated cells, but there was a difference in the expressed activation markers. Our results suggest...
Statistical data indicate a chronic shortage of work-force due to overwork, ill health state and ... more Statistical data indicate a chronic shortage of work-force due to overwork, ill health state and increased risk of chronic noninfectious diseases in Hungarian health care personnel, which needs investigations in order to decrease the risk. Nurses of oncology units, often exposed to carcinogens when preparing and handling cytostatic drugs, are especially at high risk. In the present publication we report a complex clinical, geno- and immunotoxicology risk assessment of altogether 500 nurses, performed during the last 10 years at various oncology units in Hungary. The obtained results indicate that the health status of nurses at oncology units is better than the Hungarian average, especially of hypertonia and type II diabetes. However, the prevalence of iron deficiency anemia and different thyroid gland diseases is significantly higher than those of the controls matched for sex and age. The results suggest that iron deficiency can potentiate the resistance to insulin, i.e. the persist...
Introduction: The comet assay is a fluorescent microscopic method that is able to detect DNA stra... more Introduction: The comet assay is a fluorescent microscopic method that is able to detect DNA strand-breaks even in non-proliferative cells in samples with low cell counts. Aim: The aim of the authors was to measure genotoxic DNA damage and assess oxidative DNA damage caused by occupational exposure in groups exposed to benzene, polycyclic aromatic carbohydrates and styrene at the workplace in order to clarify whether the comet assay can be used as an effect marker tool in genotoxicology monitoring. Method: In addition to the basic steps of the comet assay, one sample was treated with formamido-pirimidine-DNA-glycolase restriction-enzyme that measures oxidative DNA damage. Results: An increase was observed in tail moments in each group of untreated and Fpg-treated samples compared to the control. Conclusions: It can be concluded that occupational exposure can be detected with the method. The comet assay may prove to be an excellent effect marker and a supplementary technique for moni...
Mutation Research/Genetic Toxicology and Environmental Mutagenesis, 1999
Ž. Ž Premature early centromere division PCD, i.e., the separation of centromeres during the prom... more Ž. Ž Premature early centromere division PCD, i.e., the separation of centromeres during the prometaphasermetaphase of. the mitotic cycle seems to be a possible manifestation of chromosome instability in human chromosome-breakage Ž. syndromes. Chromosome instability also frequently occurs in the peripheral blood lymphocytes PBL of humans occupationally exposed to clastogenic agents, and is considered an etiologic factor of neoplastic diseases. In order to investigate the importance of PCD in cancer risk assessment, we studied the frequency of PCDs in PBL of 400 Hungarian subjects. The various groups comprised 188 control donors and 212 subjects occupationally exposed to different genotoxic Ž. Ž. Ž. chemicals, such as acrylonitrile ACN andror dimethylformamide DMF , benzene, cytostatic drugs, ethylene oxide ETO , mixed exposure in the rubber industry, mixed organic solvents including CCl , hot oil-mist, bitumen, and polychlorinated 4 Ž. biphenyls PCB. Data were compared with chromosomal aberration frequencies determined in the same samples. PCD yields are significantly higher in populations exposed to mixed chemicals, crude oil and cytostatic drugs, compared with controls. PCDs involving more than three chromosomes are also more frequent in ETO-and oil mist-exposed groups than in the others. The results indicate that the induction of PCDs is neither incidental nor artificial. As a consequence, we suggest that PCD can be developed into a new, exposure-related cytogenetic biomarker for a more adequate occupational cancer risk assessment. A further, follow-up epidemiological and cytogenetic investigation of PCD is in progress.
Cytogenetical endpoints, i.e., chromosome aberration (CA), sister‐chromatid exchange (SCE), and p... more Cytogenetical endpoints, i.e., chromosome aberration (CA), sister‐chromatid exchange (SCE), and proliferative rate indexes (PRI), were measured in peripheral blood lymphocytes (PBL) of 42 workers exposed occupationally to low‐dose benzene, and of 42 controls. The role of smoking habit as a confounding factor of genotoxic effects caused by occupational low‐dose benzene exposure was also studied. The benzene concentrations in the ambient air samples varied from 3 to 20 mg/m3 (mean: 7 mg/m3). The continuous low‐dose benzene exposure significantly increased the CA and SCE frequencies, but did not influence PRI. Smoking levels were characterized by subjective accounts and by serum thiocyanate concentrations (SCN). CA and SCE were not significantly increased in smokers compared to nonsmokers, but the differences were expressed to a greater extent in the case of measurement of SCN concentrations. Determination of SCN proved to be more objective in the assessment of genotoxic effects of smo...
In order to investigate the genotoxic effects of occupational acrylonitrile (ACN) and dimethylfor... more In order to investigate the genotoxic effects of occupational acrylonitrile (ACN) and dimethylformamide (DMF) exposures, clinical serum and urine parameters and genotoxicological endpoints such as chromosome aberration (CA), sister chromatid exchange (SCE), high frequency SCE (HFC), cell cycle kinetics, and UV-induced unscheduled DNA synthesis (UDS) were followed up three times during a 20-month period in peripheral blood lymphocytes (PBL) of 26 workers (13 maintainers and 13 fiber producers) occupationally exposed to ANC and/or DMF in a viscose rayon plant, 26 matched control subjects, and six industrial controls (all males). Six of the 26 exposed subjects were hospitalized because of liver dysfunction that had developed due to inhalative DMF exposure. The rate of smoking was estimated on the basis of serum thiocyanate (SCN) levels. Average peak air ACN and DMF concentrations were over the maximum concentration limits at the time of both investigations. Urine ACN and monomethyl-formamide (MMF) excretions of the exposed subjects were almost doubled after work shifts. An increase in lymphocyte count (in months 0 and 7), and severe alterations in the liver function were observed in the exposed subjects. In PBLs the proliferative rate index (PRI) was already increased in month 0 compared with the controls. In each study, significant increases in CA and SCE frequencies, as well as increases in UDS were found in PBLs of the exposed subjects. The frequencies of chromatid breaks and acentric fragments further increased in month 7 and remained constantly elevated in month 20. Increased yields of both chromatid and chromosome-type exchange aberrations first appeared in month 20, when HFCs were 2.72 times more frequent in fiber producers than in maintainers. The role of some important biological confounding factors (age, white blood cell count, and hematocrit) and lifestyle confounding factors (smoking and drinking habits) were subjected to an analysis of variance during the second study. Increased CA, SCE, and UDS were found both in control and exposed smokers when current smoking was established on the basis of the serum SCN levels. The cytogenetic data suggest that occupational exposures to ACN and DMF induce considerable genotoxic consequences and may increase the cancer risk in the exposed human populations.
Health is more than the absence of illness. It is a physical and psychological balance with the e... more Health is more than the absence of illness. It is a physical and psychological balance with the external and internal environment. Maintaining health is only possible with active and health conscious behaviour. A passive life style and the abuse of substances considerably decrease life expectancy. Maintaining health requires constant attention, work and learning. A health conscious life has to be started in the early years. Most chronic diseases develop early. The socialisation and behavioural patterns of childhood and puberty define the health of a person in the long run. The basis for a healthy life is appropriate nutrition and physical exercise. Excessive consumption of substances severely burdens the organism. Legal drugs such as cigarettes and alcohol are particularly harmful. Smoking causes perhaps the most damages in the human organism, it is the starting point of a number of respiratory and circulatory diseases. A healthy life style can be achieved in many ways. Conscious nu...
Genotoxicological investigations serve as tools to detect the damages caused by the environmental... more Genotoxicological investigations serve as tools to detect the damages caused by the environmental and occupational mutagens and carcinogens acquired by the somatic cells. These damages are well demonstrated in the course of genotoxicological monitoring by chromosomal mutation, sister chromatid exchange (SCE), and the blastic transformation activity of peripheral blood lymphocytes (PBL), among workers who were exposed to benzene and heavy metals. Workers exposed to different concentration of benzene were monitored for over 20 years. These studies showed an increase of the chromosomal aberrations in workers exposed to benzene above the 1 ppm. At the same time, parallel to the lowering of benzene levels, a decrease in the cytogenetic parameters to the level of the industrial control was observed, during the active preventional period. The main point of intervention was the improvement of the work-sites including lowering the benzene exposure and convincing the workers to change their life styles avoiding confounding factors (e.g. drugs, alcohol, medication and smoking). This monitoring system was also used to determine the protective effects of some natural products with known antioxidant capacity against the in vivo genotoxic effects of these pollutants. In the case of heavy metal (precious metals, chromium, cadmium and nickel) exposed workers, after a chemoprevention treatment with the nutritional supplement Humetta® containing various antioxidants and chelating agents, the results showed a decrease in genotoxic effects, together with improved health status based on the clinical laboratory data.
N-Nitrosodialkylamines are a unique class of environmental carcinogens which can cause tumors in ... more N-Nitrosodialkylamines are a unique class of environmental carcinogens which can cause tumors in rodents in a very organ specific manner. The mechanisms for these properties still await clarification. Possible involved parameters could be an organ specific metabolic activation, or the pharmacokinetics of the compounds or of the reactive intermediates. Furthermore, the repair mechanisms, which consequently govern the persistance of specific types of DNA damage may also play an important role. We are presently studying in which manner these individual mechanisms may contribute to organ specific effects of nitrosamines. This is done by assessing their genotoxicity in different organs. In this report, we will present some in vitro and in vivo data on the activities of N-nitrosodimethylamine (NDMA).
A toxikológia a xenobiotikumok és az endogén fiziológiai folyamatok okozta mérgező hatások tudomá... more A toxikológia a xenobiotikumok és az endogén fiziológiai folyamatok okozta mérgező hatások tudománya. Empirikus előzményei visszavezetnek az emberré válás folyamatáig, hiszen eleink életben maradásának egyik fontos záloga volt az ehető és a mérgező növények, illetve állatok elkülönítése. Az emberiség fejlődésének kiteljesedő folyamatában a mérgek használata három fő területen jelent meg: 1) a vadászatban, majd a hadviselésben, 2) békeidőben az ellenfelek megmérgezésében, miután a rejtőzködő stratégia jellemzően előnyösebbnek bizonyult a nyíltan alkalmazott durva fizikai eszközöknél, és 3) a gyógyászatban az ellenmérgek, majd a betegségeket legyőző erős anyagok révén, de paradox módon az orvoslási segédlettel végrehajtott emberölést, vagyis az aktív eutanáziát is idesorolhatjuk. A XIX. század ipari forradalma az addig marginális foglalkozási ártalmakat népbetegséggé tette, majd a vegyipar forradalma és a műanyagok tömegtermelése a XXI. században globális környezeti katasztrófával fenyegeti az emberiséget. Ez a változás a humántoxikológia után az ökológiai toxikológia színrelépését eredményezte, ami már nem történelme, hanem jövője ennek a tudománynak.
Several biomarkers may be used to detect harmful exposure and individual susceptibility to cancer... more Several biomarkers may be used to detect harmful exposure and individual susceptibility to cancer. Monitoring of biomarkers related to exposure may have a significant effect on early detection of cell transformation, thereby aiding the primary prevention of various chronic and malignant diseases. Nurses who handle cytotoxic drugs are exposed to carcinogenic agents, which have the potential to interrupt the cell cycle and to induce chromosomal aberrations. The presence of high chromosomal aberrations indicates the need for intervention even when exposure to these carcinogens is low. Nationally representative samples of 552 nurses were investigated by a follow-up monitoring system. The measured biomarkers were clinical laboratory routine tests, completed with genotoxicological (chromosome aberrations [CAs] and sister chromatid exchanges [SCEs]) and immunotoxicological monitoring (ratio of lymphocyte subpopulations and lymphocyte activation markers) measured on peripheral blood lymphoc...
More than half of the Hungarian population is overweight or obese, therefore, non-alcoholic fatty... more More than half of the Hungarian population is overweight or obese, therefore, non-alcoholic fatty liver is a common problem. According to clinical experience, 20-30% of fatty liver cases is not related to alcohol, but can be linked to diabetes, obesity or metabolic syndrome. The authors studied the correlation between genotoxicity, immuntoxicity and non-alcoholic fatty liver among oil refinery workers. During this genotoxicological monitoring study the data of 107 exposed were compared to 67 controls. 36% of oil refinery workers had non-alcoholic fatty liver, while none of the selected, non-exposed controls had this abnormality. Chromosomal aberrations were elevated from 1.6% to 3.75% in the exposed group, immunotoxicological parameters were also changed, and CD71 positive B-cell ratio increased especially among subjects having non-alcoholic fatty liver. Non-alcoholic fatty liver can negatively influence the genotoxic effects of environmental hazards in workplaces. In the future thi...
Introduction 1.1 Environmental endogenous DNA damages Cancer development is a long-term, multiste... more Introduction 1.1 Environmental endogenous DNA damages Cancer development is a long-term, multistep process with a complex interplay between genes and environment. The magnitude of environmental effects depends on the presence or absence of genetic susceptibility of the subjects to certain cancer types. Molecular epidemiological studies in cancer have proved that besides target cell genetic instability, the presence of triggering environmental exposure is critical in cancer development [Albertini & Hayes 1997, Newby & Howard 2005]. The biomarker responses, exposure character and the route of exposure of different environmental factors (chemicals, physical agents and biological agents) are also important in causing tumors especially in the cases of occupational cancer [Ward 1995]. The EPA Guidelines for carcinogen Risk Assessment [EPA 2005] is based on the mode of action of chemicals, such as interaction with DNA, cytotoxicity, or binding to the receptors modifying signal pathways. There are several natural compounds-so called chemopreventive agents-which are able to modify the genotoxic or mutagenic response (Ames 1983) in different organisms. These vitamins, antioxidants, phytochemicals, micro nutrients are available on the market without knowing their mode of action. Mutagenesis caused by environmental chemicals or physical agents can be prevented by protection of the cell's DNA replication, increasing the repair capacity or delaying cell replication to allow enough time to make a complete repair of damaged cells. Antioxidants are able to protect the cells from oxidative stress, and stimulate the phase I reactions including oxidation, reduction, and hydrolysis of xenobiotics by the monoxigenase detoxicating key enzymes, such as CYP450 [Xu et al. 1996, Poulsen & Loft 1998]. These changes increase the polarity of these molecules and help to conjugate them in phase II to glucuronic acid, acetic acid and sulfuric acid which are the physiological ways to eliminate active metabolites that are genotoxic to the target cells. The best studied crucial early event in carcinogenesis is chromosomal aberration, including microsatellite instability, abnormal number of chromosomes (aneuploidy), gene amplification or the loss of heterozygosity of tumor suppressor genes. By reducing chromosomal mutation via chemoprevention, the cell may be able to survive the genotoxic effects without any permanent damage, or it is able to go through the physiological pathway of apoptosis, without mutation occurring in the P53 gene [Lowe & Lin 2000]. www.intechopen.com DNA Repair and Human Health 308 1.2 The role of DNA repair in gene-environmental interactions The measurement of UV-induced DNA repair is recommended in the risk assessment of environmental exposure to harmful chemicals (Reg. 440/2008/EC). Data obtained on prokaryota organisms suggest that exposure to chemicals as e.g. free oxygen radicals can interact with UV-induced DNA repair mechanisms (Chandor-Proust et al, 2008). Among the repair mechanisms existing in higher eukaryota, base excision repair (BER) seems to be the main mechanism involved in the removal of lesions produced by alkylation, deamination or oxidation (Rastogi et al, 2010). Orelli et al. (2009) demonstrated recently that nucleotide excision repair (NER) also plays an important role in the development of cisplatin resistance. UV-induced DNA damages can induce the so called three prime exonuclease1 (trex1), as a response to genotoxic stress. Beside thymine dimer production, UV irradiation can also produce reactive oxygen species. Benzo(a)pyrene (BaP) and hydrogen peroxide may, similarly to UV, induce the so-called three prime exonuclease1 (trex1) involved in the repair pathways of UV-induced DNA lesions, and cells deficient in trex1 show reduced recovery from UV and BaP replication inhibition, and increased sensitivity to towards genotoxins compared to the isogenic control (Christmann et al, 2010). These data suggest that both main mechanisms can be involved in the total repair of environmental chemical-induced genotoxic stress. Such mechanisms can probably explain the observed UDS reduction in some of our groups exposed to various chemicals but not UV. A second question is whether decreased UDS can be related to an increase in apoptotic capacity? Cells deficient in the repair of UV-induced DNA damage can be more susceptible to a G1 arrest after UV treatment than cells with normal repair capacity or those cells which have completed their DNA repair prior to movement from G1 to S phase (Geyer et al, 2000). Zampetti-Bosseler and Scott (1981) demonstrated a prolonged mitotic delay in repair deficient ataxia teleangiectasia and retinoblastoma fibroblasts after X-ray irradiation compared to normal human fibroblasts, also suggesting a general key role of cell cycle check points beside DNA repair in preservation of genome stability (Kaufman, 1995). Skin fibroblasts from derived ataxia teleangiectasia patients are also more sensitive to UVinduced mutagenesis than those taken from healthy subjects (Hannan et al, 2002), and their results suggested a relationship between cell cycle control and DNA repair pathways in human cells. Genotoxic chemicals can also delay cellular proliferation in DNA repairdeficient cell clones more significantly than in wild type cells, by interfering with DNA replication, thereby inducing DNA damage (Kyunghee et al, 2009). The recently discovered cell cycle checkpoint activation mechanisms are discussed in detail by Rastogi et al (2010). In the present study the so-called premature centromere division (PCD) was used as a cytogenetic indicator of abnormalities in cell cycle regulation (Méhes 1978, Vig, 1981, Major et al, 1999). PCD yields were increased among cytostatic drug producers, anesthesiologists using halothane, and in exposures to formaldehyde, benzene and PAHs. PCD can be involved in the pathomechanism of aneuploidy, it seems to be a possible manifestation of chromosome instability also in human chromosome breakage syndromes and it can be connected with carcinogenesis (for review, c.f. Major et al, 1999). 2. Cancer development and DNA repair We don't know exactly what the cause of cancer is; therefore we have several mechanisms and theories to explain it. One of them is shown in Fig.1. www.intechopen.com Application of UV-Induced Unscheduled DNA-Synthesis Measurements in Human Genotoxicological Risk Assessment 315 6. Analysis of biomarkers in blood samples Biomarkers for DNA damages and risk assessment Considering the basic mechanism of cancer development, the most acceptable predictors of cancer risks are the DNA-damage biomarkers (see Table 3.). These damages can be provoked by exogenous or end o g e n o u s a g e n t s w h e n D N A r e p a i r o r m i s-r e p a i r i s i n dysfunction. The unrepaired DNA damage can reduce the basic cell functions eg. maintenance of genetic integrity, triggering of cell cycle arrest, apoptosis, uncontrolled growth and other functionalities. Ultimately, damaged repair capacity leads to an increase in somatic mutations and cancer. Any living cells Mitochondrial DNA mutation Any living cells Point mutation (HPRT) Any living cells Nuclear p53 Lymphocytes, germ cells DNA-adducts and oxidation, methylation Any living cells Telomere shortening Tumor cells, lymphocytes, germ cells Aneuploidy Lymphocytes, bone marrow cells Micronucleus assay Tumor cells, lymphocytes, germ cells Chromosomal aberrations Any living cells, germ cells DNA strand breaks (SGE or Comet assay) Lymphocytes, hepatocytes Unscheduled DNA synthesis (UDS) Target cells Methods Any living cells Mitochondrial DNA mutation Any living cells Point mutation (HPRT) Any living cells Nuclear p53 Lymphocytes, germ cells DNA-adducts and oxidation, methylation Any living cells Telomere shortening Tumor cells, lymphocytes, germ cells Aneuploidy Lymphocytes, bone marrow cells Micronucleus assay Tumor cells, lymphocytes, germ cells Chromosomal aberrations Any living cells, germ cells DNA strand breaks (SGE or Comet assay) Lymphocytes, hepatocytes Unscheduled DNA synthesis (UDS)
At the National Institute of Chemical Safety we have surveyed the immunological status of donors ... more At the National Institute of Chemical Safety we have surveyed the immunological status of donors from the oil industry, health services, and metallurgy exposed to different immunotoxic compounds. Their data were compared to those of healthy, non-exposed controls. Our aim was to study the relationship between immunotoxic exposure and immune function, and to establish a system of immunological parameters by which chemical exposure can be specifically monitored. Subpopulations and activation of lymphocytes was measured by flow cytometry, using immunophenotyping of peripheral blood lymphocytes. In the groups exposed to immunotoxic compounds we found an increase in helper, and a decrease in cytotoxic T lymphocytes, leading to a shift in Th/Tc ratios. These phenomena are not substance specific, but relate to chemical exposure. The lymphocytes of exposed groups showed a higher proportion of activated cells, but there was a difference in the expressed activation markers. Our results suggest...
Statistical data indicate a chronic shortage of work-force due to overwork, ill health state and ... more Statistical data indicate a chronic shortage of work-force due to overwork, ill health state and increased risk of chronic noninfectious diseases in Hungarian health care personnel, which needs investigations in order to decrease the risk. Nurses of oncology units, often exposed to carcinogens when preparing and handling cytostatic drugs, are especially at high risk. In the present publication we report a complex clinical, geno- and immunotoxicology risk assessment of altogether 500 nurses, performed during the last 10 years at various oncology units in Hungary. The obtained results indicate that the health status of nurses at oncology units is better than the Hungarian average, especially of hypertonia and type II diabetes. However, the prevalence of iron deficiency anemia and different thyroid gland diseases is significantly higher than those of the controls matched for sex and age. The results suggest that iron deficiency can potentiate the resistance to insulin, i.e. the persist...
Introduction: The comet assay is a fluorescent microscopic method that is able to detect DNA stra... more Introduction: The comet assay is a fluorescent microscopic method that is able to detect DNA strand-breaks even in non-proliferative cells in samples with low cell counts. Aim: The aim of the authors was to measure genotoxic DNA damage and assess oxidative DNA damage caused by occupational exposure in groups exposed to benzene, polycyclic aromatic carbohydrates and styrene at the workplace in order to clarify whether the comet assay can be used as an effect marker tool in genotoxicology monitoring. Method: In addition to the basic steps of the comet assay, one sample was treated with formamido-pirimidine-DNA-glycolase restriction-enzyme that measures oxidative DNA damage. Results: An increase was observed in tail moments in each group of untreated and Fpg-treated samples compared to the control. Conclusions: It can be concluded that occupational exposure can be detected with the method. The comet assay may prove to be an excellent effect marker and a supplementary technique for moni...
Mutation Research/Genetic Toxicology and Environmental Mutagenesis, 1999
Ž. Ž Premature early centromere division PCD, i.e., the separation of centromeres during the prom... more Ž. Ž Premature early centromere division PCD, i.e., the separation of centromeres during the prometaphasermetaphase of. the mitotic cycle seems to be a possible manifestation of chromosome instability in human chromosome-breakage Ž. syndromes. Chromosome instability also frequently occurs in the peripheral blood lymphocytes PBL of humans occupationally exposed to clastogenic agents, and is considered an etiologic factor of neoplastic diseases. In order to investigate the importance of PCD in cancer risk assessment, we studied the frequency of PCDs in PBL of 400 Hungarian subjects. The various groups comprised 188 control donors and 212 subjects occupationally exposed to different genotoxic Ž. Ž. Ž. chemicals, such as acrylonitrile ACN andror dimethylformamide DMF , benzene, cytostatic drugs, ethylene oxide ETO , mixed exposure in the rubber industry, mixed organic solvents including CCl , hot oil-mist, bitumen, and polychlorinated 4 Ž. biphenyls PCB. Data were compared with chromosomal aberration frequencies determined in the same samples. PCD yields are significantly higher in populations exposed to mixed chemicals, crude oil and cytostatic drugs, compared with controls. PCDs involving more than three chromosomes are also more frequent in ETO-and oil mist-exposed groups than in the others. The results indicate that the induction of PCDs is neither incidental nor artificial. As a consequence, we suggest that PCD can be developed into a new, exposure-related cytogenetic biomarker for a more adequate occupational cancer risk assessment. A further, follow-up epidemiological and cytogenetic investigation of PCD is in progress.
Cytogenetical endpoints, i.e., chromosome aberration (CA), sister‐chromatid exchange (SCE), and p... more Cytogenetical endpoints, i.e., chromosome aberration (CA), sister‐chromatid exchange (SCE), and proliferative rate indexes (PRI), were measured in peripheral blood lymphocytes (PBL) of 42 workers exposed occupationally to low‐dose benzene, and of 42 controls. The role of smoking habit as a confounding factor of genotoxic effects caused by occupational low‐dose benzene exposure was also studied. The benzene concentrations in the ambient air samples varied from 3 to 20 mg/m3 (mean: 7 mg/m3). The continuous low‐dose benzene exposure significantly increased the CA and SCE frequencies, but did not influence PRI. Smoking levels were characterized by subjective accounts and by serum thiocyanate concentrations (SCN). CA and SCE were not significantly increased in smokers compared to nonsmokers, but the differences were expressed to a greater extent in the case of measurement of SCN concentrations. Determination of SCN proved to be more objective in the assessment of genotoxic effects of smo...
In order to investigate the genotoxic effects of occupational acrylonitrile (ACN) and dimethylfor... more In order to investigate the genotoxic effects of occupational acrylonitrile (ACN) and dimethylformamide (DMF) exposures, clinical serum and urine parameters and genotoxicological endpoints such as chromosome aberration (CA), sister chromatid exchange (SCE), high frequency SCE (HFC), cell cycle kinetics, and UV-induced unscheduled DNA synthesis (UDS) were followed up three times during a 20-month period in peripheral blood lymphocytes (PBL) of 26 workers (13 maintainers and 13 fiber producers) occupationally exposed to ANC and/or DMF in a viscose rayon plant, 26 matched control subjects, and six industrial controls (all males). Six of the 26 exposed subjects were hospitalized because of liver dysfunction that had developed due to inhalative DMF exposure. The rate of smoking was estimated on the basis of serum thiocyanate (SCN) levels. Average peak air ACN and DMF concentrations were over the maximum concentration limits at the time of both investigations. Urine ACN and monomethyl-formamide (MMF) excretions of the exposed subjects were almost doubled after work shifts. An increase in lymphocyte count (in months 0 and 7), and severe alterations in the liver function were observed in the exposed subjects. In PBLs the proliferative rate index (PRI) was already increased in month 0 compared with the controls. In each study, significant increases in CA and SCE frequencies, as well as increases in UDS were found in PBLs of the exposed subjects. The frequencies of chromatid breaks and acentric fragments further increased in month 7 and remained constantly elevated in month 20. Increased yields of both chromatid and chromosome-type exchange aberrations first appeared in month 20, when HFCs were 2.72 times more frequent in fiber producers than in maintainers. The role of some important biological confounding factors (age, white blood cell count, and hematocrit) and lifestyle confounding factors (smoking and drinking habits) were subjected to an analysis of variance during the second study. Increased CA, SCE, and UDS were found both in control and exposed smokers when current smoking was established on the basis of the serum SCN levels. The cytogenetic data suggest that occupational exposures to ACN and DMF induce considerable genotoxic consequences and may increase the cancer risk in the exposed human populations.
Health is more than the absence of illness. It is a physical and psychological balance with the e... more Health is more than the absence of illness. It is a physical and psychological balance with the external and internal environment. Maintaining health is only possible with active and health conscious behaviour. A passive life style and the abuse of substances considerably decrease life expectancy. Maintaining health requires constant attention, work and learning. A health conscious life has to be started in the early years. Most chronic diseases develop early. The socialisation and behavioural patterns of childhood and puberty define the health of a person in the long run. The basis for a healthy life is appropriate nutrition and physical exercise. Excessive consumption of substances severely burdens the organism. Legal drugs such as cigarettes and alcohol are particularly harmful. Smoking causes perhaps the most damages in the human organism, it is the starting point of a number of respiratory and circulatory diseases. A healthy life style can be achieved in many ways. Conscious nu...
Genotoxicological investigations serve as tools to detect the damages caused by the environmental... more Genotoxicological investigations serve as tools to detect the damages caused by the environmental and occupational mutagens and carcinogens acquired by the somatic cells. These damages are well demonstrated in the course of genotoxicological monitoring by chromosomal mutation, sister chromatid exchange (SCE), and the blastic transformation activity of peripheral blood lymphocytes (PBL), among workers who were exposed to benzene and heavy metals. Workers exposed to different concentration of benzene were monitored for over 20 years. These studies showed an increase of the chromosomal aberrations in workers exposed to benzene above the 1 ppm. At the same time, parallel to the lowering of benzene levels, a decrease in the cytogenetic parameters to the level of the industrial control was observed, during the active preventional period. The main point of intervention was the improvement of the work-sites including lowering the benzene exposure and convincing the workers to change their life styles avoiding confounding factors (e.g. drugs, alcohol, medication and smoking). This monitoring system was also used to determine the protective effects of some natural products with known antioxidant capacity against the in vivo genotoxic effects of these pollutants. In the case of heavy metal (precious metals, chromium, cadmium and nickel) exposed workers, after a chemoprevention treatment with the nutritional supplement Humetta® containing various antioxidants and chelating agents, the results showed a decrease in genotoxic effects, together with improved health status based on the clinical laboratory data.
N-Nitrosodialkylamines are a unique class of environmental carcinogens which can cause tumors in ... more N-Nitrosodialkylamines are a unique class of environmental carcinogens which can cause tumors in rodents in a very organ specific manner. The mechanisms for these properties still await clarification. Possible involved parameters could be an organ specific metabolic activation, or the pharmacokinetics of the compounds or of the reactive intermediates. Furthermore, the repair mechanisms, which consequently govern the persistance of specific types of DNA damage may also play an important role. We are presently studying in which manner these individual mechanisms may contribute to organ specific effects of nitrosamines. This is done by assessing their genotoxicity in different organs. In this report, we will present some in vitro and in vivo data on the activities of N-nitrosodimethylamine (NDMA).
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